INTRODUCTION<\/strong><\/p>\n Hashimoto\u2019s thyroiditis (HT), also called chronic lymphocytic or autoimmune thyroiditis, is part of the spectrum of autoimmune thyroid diseases (AITD) and is associated with various degrees of thyroid hypofunction and circulating antibodies to thyroid antigens.1,2 <\/sup>By strict criteria, it is a histologic diagnosis that was first described by Hakaru Hashimoto, a Japanese surgeon working in Berlin, Germany.3<\/sup> The cause of HT is thought to be a combination of genetic susceptibility and environmental factors.4<\/sup> The incidence of HT is estimated to be 10-15 times higher in females; its annual incidence worldwide is estimated to be 0.3-1.5 cases per 1000 individuals.5<\/sup> In clinical practice, patients (especially women) with HT and a firm, solitary, \u201ccold\u201d thyroid nodule on radionuclide scanning should have an ultrasound-guided fine needle aspiration biopsy (FNAB) because of the potentially increased risk of a concurrent thyroid cancer (TC).1<\/sup> Although the link between chronic inflammation and cancer is well established, the association between HT and papillary thyroid carcinoma (PTC) has been controversial in medical bibliography since its initial description by Dailey et al in 1955.6-21<\/sup> The aim of our study was to determine the prevalence of PTC and HT coexistence in histopathologic material of thyroidectomized patients.<\/p>\n PATIENTS AND METHODS<\/strong><\/p>\n In a retrospective study, we analyzed clinicohistopathologic data of 140 patients (19 males\/121 females), mean age 52 (range 16-74) years, who underwent a total or near total thyroidectomy for any thyroid pathology from January 2005 to December 2009 at the Naval Hospital of Crete, Chania, Greece. All patients were from the region of Chania. The diagnosis of TC was confirmed either by the re-evaluation of histopathology sections, when available, or from reviews of the pathology reports. TC classification was based on the TNM classification system.22<\/sup> Coexistent HT was defined as the presence of diffuse lymphocytic and plasma cell infiltrate, oxyphilic cells and the formation of lymphoid follicles and reactive germinal centres; the infiltrate had to occur in a normal region of the thyroid gland, distinct from the site of the TC. Peritumoural inflammatory response was not designated as HT. Tumour recurrence was defined as new evidence of TC (locoregional or distant metastasis) after successful tumour resection in which postoperative serum thyroglobulin levels were normal for at least six months or the postoperative radioiodine scan was negative (or both). Persistent TC was defined as an elevated postoperative serum thyroglobulin or persistent uptake on the postoperative radioiodine scan after thyroidectomy and radioiodine ablation treatment. The potential association of PTC with HT in histopathologic material was assessed by the use of the \u03c72-test. Time-independent variables were evaluated using Student\u2019s t-test. The differences were considered statistically significant at p<0.05.<\/p>\n RESULTS<\/strong><\/p>\n The reasons for thyroidectomy and the prevalence of histopathologic diagnoses among the 140 thyroidectomized patients are presented in Tables 1<\/a> and 2<\/a> . 32 of the 33 thyroidectomized patients with TC had PTC. The stage of PTC (TNM system) at the time of diagnosis was I (4 patients with T1aN0M0 and 28 patients with T1bN0M0; T1a: tumour diameter 1cm or less, T1b: tumour diameter of more than 1cm but not more than 2cm, N0: no regional lymph node matastasis, M0: no distant metastasis). The association of PTC with HT in histopathologic material in our patients is presented in Table 3<\/a> . HT was found in 42 (30%) of the 140 specimens (7 males, 16.7% and 35 females, 83.3%). PTC was found in 32 (22.9%) of the 140 specimens, (7 males, 21.9% and 25 females, 78.1%). Coexistence of HT and PTC was detected in 12 (8.6%) of the 140 specimens, (3 males, 25% and 9 females, 75%). Among 32 specimens with PTC, the prevalence of HT was 37.5%, which is higher than the prevalence of HT in other specimens without PTC (27.7%). Among 42 specimens with HT, the prevalence of PTC was 28.6%, which is higher than the prevalence of PTC in other specimens without HT (20.4%). However, there was no statistically significant difference (\u03c72=1.11, df=1, p=0.29) between the presence of PTC in specimens with HT and the presence of PTC in other HT negative specimens (Table 3<\/a>). The majority of thyroidectomized patients with HT or PTC were females (35 females versus 7 males and 25 females versus 7 males, respectively); there was no statistically significant gender difference (\u03c72=0.49, df=1, p=0.48) or PTC (\u03c72=2.43, df=1, p=0.12).<\/p>\n The available clinicopathologic features of the 32 PTC patients with and without HT are summarized in Table 4<\/a> . The majority of PTC patients were females (25 female versus 7 male); there was no statistically significant gender difference between PTC patients with and without HT (\u03c72=0.11, df=1, p=0.74). In addition, there was no significant difference in age (t=1.36, df=30, p=0.18) or tumour size (\u03c72=0.305, df=1, p=0.58) at the time of diagnosis between PTC patients with and without HT. The number of PTC patients with tumour size \u226410mm was the same among the two groups (HT present and HT absent). Follow-up data revealed no persistent or recurrent PTC. No deaths were observed among patients with PTC from the time of diagnosis to the last follow-up examination (mean\u00b1SD is 3.7\u00b11.6 years).<\/p>\n